BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates generally to acoustic structures that are used to attenuate
noise that emanates from a specific source. More particularly, the present invention
is directed to providing an acoustic structure in which acoustic septa are located
in the cells of a honeycomb for reducing the noise generated from a source. The acoustic
structure may be contoured to form acoustic structures having tight radii of curvatures
and/or compound curvatures.
2. Description of Related Art
[0002] It is widely recognized that the best way of dealing with excess noise generated
by a specific source is to treat the noise at the source. This is typically accomplished
by adding acoustic damping structures (acoustic treatments) to the structure of the
noise source. One particularly problematic noise source is the jet engine used on
most passenger aircraft. Acoustic treatments are typically incorporated in the engine
inlet, nacelle and exhaust structures. These acoustic treatments include acoustic
resonators that contain relatively thin acoustic materials or grids that have millions
of holes that create acoustic impedance to the sound energy generated by the engine.
[0003] Honeycomb has been a popular material for use in aircraft and aerospace vehicles
because it is relatively strong and lightweight. For acoustic applications, such as
engine nacelles, acoustic materials are added to the honeycomb structure so that the
honeycomb cells are acoustically closed with a solid sound impermeable sheet or skin
at the end located away from the engine and covered with a porous or perforated sound
permeable covering at the end located closest to the engine. The closing of the honeycomb
cells with acoustic material in this manner creates an acoustic resonator that provides
attenuation, damping and/or suppression of the noise. Acoustic septums are also usually
incorporated into the interior of the honeycomb cells in order to provide the resonator
with additional noise attenuation properties.
[0004] One way of incorporating acoustic septums into the honeycomb cells is to first form
planar acoustic inserts from an acoustic material, such as an acoustic mesh or perforated
acoustic film. The planar acoustic inserts are made larger than the cell openings.
Accordingly, when the inserts are pushed into the cells with a plunger, they are folded
into an acoustic septum in the form of a cap. The cap shape provides an anchoring
portion that contacts the cell walls and a central septum portion which attenuates
the sound waves in the cell. Once inserted into the cells, the friction between the
anchoring portion of the acoustic septum cap and the honeycomb walls temporarily locks
the acoustic septum cap in place. An adhesive is then applied to permanently bond
the anchoring portions of the inserted acoustic septum caps to the cell walls.
[0005] The permanent bonding of the acoustic septum caps is typically accomplished by dipping
the entire honeycomb into a pool of liquid adhesive. The depth to which the honeycomb
is dipped into the adhesive is chosen so that the anchoring portions of the inserted
acoustic septum caps are immersed in the liquid adhesive. This adhesive dip process
is particularly effective because it provides simultaneous bonding of the many hundreds
of acoustic septums that are located within a typical acoustic honeycomb.
[0006] The insertion of septum caps into honeycomb to form an acoustic honeycomb is described
in
United States Patents Nos. 7,434,659;
7,510,052,
7,854,298 and
9,016,430. As set forth in these issued patents, friction-locking of the septum caps is an
important aspect of the septum-insertion procedure. For example, the septums may shift
or otherwise move during handling if friction-locking is not adequate. Any shifting
of the septums makes it difficult to apply adhesive uniformly to the septums during
bonding. Shifting of the septums also causes uncontrolled altering of the acoustic
properties. In the worst case, the septum may fall completely out of the honeycomb
cell if friction locking is not adequate.
[0007] The majority of honeycomb used in acoustic treatments have hexagonal cells. Such
hexagonal honeycomb tends to be stiff and can be difficult to form into curved structures
without buckling the cell walls. In most cases, curved acoustic structures are made
by seaming together multiple sections of hexagonal acoustic honeycomb. Flexible honeycomb
is available which can be formed into structures with tight radii of curvature and
compound curves. Flex-Core® honeycomb is a type of flexible honeycomb that is available
from Hexcel Corporation (Dublin, CA). Flex-Core® honeycomb has a unique cell configuration
in which the cell walls include convex and concave curvatures. The unique combination
of convex and concave cell wall curvatures, as well as other cell design features
of Flex-Core® honeycomb, impart flexibility and formability to the honeycomb so that
structures with tight radii and/or compound curvatures can be formed with reduced
anticlastic curvature and without buckling the cell walls.
[0008] The inherent flexibility of Flex-Core® honeycomb makes it a desirable honeycomb for
use in making acoustic structures where tight radii of curvature and/or compound curvatures
are required. However, the unique cell configuration of Flex-Core® honeycomb presents
complex challenges with respect to the insertion of a septum cap style acoustic septum
into the cell.
[0009] EP09555109 discloses flexible honeycomb panels that are vented by providing vent openings at
specific locations within the honeycomb core, particularly flexible honeycomb panels
which are made from bonded corrugated sheets, wherein each of the corrugated sheets
has upper and lower node ridges and the lower surfaces of lower node ridges are bonded
to the upper surface of lower node ridges located on underlying sheets. The corrugated
sheets are stacked so that the adhesive or bond lines between the lower nodes are
displaced from each other within the stack. Vent openings are located in the upper
node ridges to provide venting of the honeycomb structure.
[0010] US7510052 discloses an acoustic structure that includes a honeycomb having cells in which septum
caps are located, wherein the septum caps are formed from sheets of acoustic material
and include a resonator portion and a flange portion. The flange portion has an anchoring
surface that provides frictional engagement of the septum caps to the honeycomb cells
when the caps are inserted into the honeycomb during fabrication of the acoustic structure,
and an adhesive is applied to the anchoring surface of the septum caps after the caps
have been inserted into the honeycomb cells to provide a permanent bond.
[0011] US9469985 discloses an acoustic structure having multiple degrees of acoustic freedom for reducing
noise generated from a source. Acoustic septum caps are an integral part of the acoustic
structure, and include depth control portions that can be varied in width so that
the septum portions of different septum caps can be located at different depths within
the acoustic structure to provide an acoustic structure having multiple degrees of
acoustic freedom even though the acoustic septum caps are anchored at the same depth
within the structure.
[0012] US9016430 discloses a honeycomb structure that includes cells in which septa are located to
provide acoustic dampening. The cells are formed by at least four walls wherein at
least two of the walls are substantially parallel to each other, and the septa include
warp fibers and weft fibers that are substantially perpendicular to each other. The
septa are oriented in the honeycomb cells such that the weft fibers and/or warp fibers
are substantially perpendicular to the parallel walls.
[0013] Hexcel Corporation, "HexWeb Honeycomb Selector Guide", 1 January 2016 is a guide
that is stated to be intended to assist with the selection of the best type of honeycomb
for a particular application, the guide includes details of a range of honeycomb products
and lists a range of materials and structures.
SUMMARY OF THE INVENTION
[0014] In accordance with the present invention, it was discovered that a particular planar
acoustic septum insert configuration is well-suited for insertion into Flex-Core®
honeycomb cells and honeycomb having similarly contoured cells. The planar acoustic
septum insert is configured to account for the unique shape of the cell contours to
provide the desired amount of friction locking when inserted into the flexible honeycomb
cell while still being able to provide desired acoustic properties after being permanently
bonded in place even when the flexible honeycomb is formed into a curved acoustic
structure.
[0015] The present invention provides an acoustic structure in which acoustic septa are
located in the cells of a honeycomb for reducing the noise generated from a source,
said acoustic structure comprising:
- A) a honeycomb comprising a first edge to be located closest to said source and a
second edge, said honeycomb comprising a cell having a left side and a right side,
said cell being defined by a lower wall that extends between said first and second
edges and an upper wall that also extends between said first and second edges, said
lower wall comprising a lower left end portion, a lower right end portion and a convex
portion located between said lower left and lower right end portions, said upper wall
comprising an upper left end portion, an upper right end portion and a concave portion
located between said upper left and upper right end portions, wherein said lower left
end portion and said upper left end portion are connected to form a left junction
along the left side of said cell and said lower right end portion and said upper right
end portion are connected to form a right junction along the right side of said cell;
- B) an acoustic septum comprising:
- a) a planar acoustic portion extending transverse to said upper and lower walls, said
planar acoustic portion having a top side located nearest to said first edge, a bottom
side located nearest to said second edge, a right boundary, a left boundary, a lower
boundary and an upper boundary;
- b) a right tab portion protruding from said acoustic portion at said right boundary;
- c) a left tab portion protruding from said acoustic portion at said left boundary;
- d) a lower tab portion protruding from said acoustic portion at said lower boundary;
- e) an upper tab portion protruding from said acoustic portion at said upper boundary;
and
- C) an adhesive that bonds said right tab portion, left tab portion, lower tab portion
and upper tab portion to said honeycomb wherein said right tab portion is bonded to
said lower right end portion and said upper right end portion, said left tab portion
is bonded to said lower left end portion and said upper left end portion, said lower
tab portion is bonded to said convex portion and said upper tab portion is bonded
to said concave portion.
[0016] The present invention further provides a method for making an acoustic structure
in which acoustic septa are located in the cells of a honeycomb for reducing the noise
generated from a source, said method comprising the steps of:
- A) providing a flexible honeycomb comprising a first edge to be located closest to
said source and a second edge, said flexible honeycomb comprising a cell having a
left side and a right side, said cell being defined by a lower wall that extends between
said first and second edges and an upper wall that also extends between said first
and second edges, said lower wall comprising a lower left end portion, a lower right
end portion and a convex portion located between said lower left and lower right end
portions, said upper wall comprising an upper left end portion, an upper right end
portion and a concave portion located between said upper left and upper right end
portions, wherein said lower left end portion and said upper left end portion are
connected to form a left junction along the left side of said cell and said lower
right end portion and said upper right end portion are connected to form a right junction
along the right side of said cell;
- B) providing a planar acoustic septum insert comprising:
- a) a planar acoustic portion having a right boundary, a left boundary, a lower boundary
and an upper boundary;
- b) a right tab portion protruding from said acoustic portion at said right boundary;
- c) a left tab portion protruding from said acoustic portion at said left boundary;
- d) a lower tab portion protruding from said acoustic portion at said lower boundary;
and
- e) an upper tab portion protruding from said acoustic portion at said upper boundary;
- C) inserting said planar acoustic septum insert into said cell to form an acoustic
septum wherein said planar acoustic portion extends transverse to said upper and lower
walls, said planar acoustic portion having a top side located nearest to said first
edge, a bottom side located nearest to said second edge; and
- D) bonding said right tab portion, left tab portion, lower tab portion and upper tab
portion to said honeycomb wherein said right tab portion is bonded to said lower right
end portion and said upper right end portion, said left tab portion is bonded to said
lower left end portion and said upper left end portion, said lower tab portion is
bonded to said convex portion and said upper tab portion is bonded to said concave
portion.
[0017] The above described and many other features and attendant advantages of the present
invention will become better understood by reference to the following detailed description
when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
FIG. 1 is a perspective view of a flexible acoustic honeycomb for use in accordance
with the present invention.
FIG. 2 shows a planar acoustic septum insert suitable for use in the present invention.
FIG. 3 shows a preferred exemplary planar acoustic septum insert.
FIG. 4 is a cross-sectional view of a single cell from the flexible honeycomb shown
in FIG. 1.
FIG. 5 is a partial perspective view of a plunger for use in inserting the planar
acoustic septum insert into the cell of a flexible honeycomb.
FIG. 6 is a simplified view showing application of adhesive to septum caps in order
to permanently bond the septum caps into the honeycomb cells.
FIG. 7 is a simplified view of a flexible acoustic structure in accordance with the
present invention in place for attenuating sound from a source of noise.
DETAILED DESCRIPTION OF THE INVENTION
[0019] A flexible acoustic honeycomb for use in an acoustic structure in accordance with
the present invention is shown generally at 10 in FIG. 1. The flexible acoustic honeycomb
10 has a lengthwise direction (L), a width direction (W) and a thickness direction
(T). The flexible acoustic honeycomb 10 includes a flexible honeycomb 12 having a
first edge 14 which is to be located nearest the noise source and a second edge 16.
The flexible acoustic honeycomb 10 has cells 18 that each have a left side 20 and
a right side 22. Each cell has a lower wall 24 that extends between the first edge
14 and second edge 16 and an upper wall 26 that also extends between the first edge
14 and second edge 16. Each of the cells 18 has a depth which is equal to the honeycomb
thickness (T) which is the distance between the two edges 14 and 16. Each cell 18
also has a cross-sectional area that is measured perpendicular to the cell walls 24
and 26.
[0020] As shown in FIGS. 1 and 4, the lower cell wall 24 has a lower left end portion 28,
a lower right end portion 30 and a convex portion 32 which is located between the
lower left end portion and lower right end portion. The upper cell wall 26 has an
upper left end portion 34, an upper right end portion 36 and a concave portion 38
which is located between the upper left end portion and upper right end portion. The
lower left end portion 28 and upper left end portion 34 are connected to form a left
junction 40 along the left side of the cell. The lower right end portion 30 and the
upper right end portion 36 are connected to form a right junction 42 along the right
side of said cell. The approximate location of the transitions between the various
portions in the upper and lower cell walls are indicated by hash marks "w", "x", "y"
and "z" in FIG. 4.
[0021] The acoustic honeycomb 10 includes septa 44. The septa 44 are formed by inserting
numerous planar acoustic septum inserts 46, as shown in FIG. 2, into the honeycomb
cells to form acoustic septum caps which are initially friction-locked in place and
then adhesively bonded to the cells to form the septa 44. It was discovered that the
shape and configuration of the acoustic septum insert must meet certain criteria,
as described below, so that the acoustic septum insert folds properly during insertion
and forms a septum cap that is adequately friction-locked in the cell and which provides
a suitable planar acoustically active central portion after the septum cap has been
adhesively bonded to the cell walls.
[0022] As shown in FIG. 2, the planar acoustic septum insert 46 is composed of a centrally
located planar acoustic portion 48 which has a perimeter or overall boundary shown
as dotted line 50. The overall boundary 50 is formed by a right boundary 52, a left
boundary 54, a lower boundary 56 and an upper boundary 58. The right boundary or right
perimeter section 52 extends between boundary markers "a" and "b". The left boundary
or left perimeter section 54 extends between boundary markers "c" and "d". The lower
boundary or lower perimeter section 56 extends between boundary markers "c" and "b".
The upper boundary or upper perimeter section 58 extends between the boundary markers
"d" and "a".
[0023] The planar acoustic portion 48 is surrounded by tabs which are folded into place
against the cell walls during insertion to provide friction-locking of the acoustic
septum insert 46 to the cell walls and to later function as anchoring tabs which are
permanently bonded to the cell walls. A right tab portion 60 protrudes from the acoustic
portion at the right boundary 52. A left tab portion 62 protrudes from the acoustic
portion at the left boundary 54. A lower tab portion 64 protrudes from the acoustic
portion at the lower boundary 56. An upper tab portion 66 protrudes from the acoustic
portion at said upper boundary 58.
[0024] The right tab portion 60 includes an outer end which has an angular perimeter with
a centrally located apex. Specifically, the angular perimeter is formed by a first
outwardly extending edge 60a and a second outwardly extending edge 60b which are oriented
at an angle (e) relative to each other such that they meet at apex 61. The left tab
portion 62 also includes an outer end which has an angular perimeter with a centrally
located apex. The angular perimeter of the outer end of the left tab portion is formed
by a first outwardly extending edge 62a and a second outwardly extending edge 62b
which are oriented at an angle (f) relative to each other such that they meet at apex
63. The angles "e" and "f' are preferably approximately equal (±5°) and may range
from 60 to 120° depending upon the specific configuration of the flexible honeycomb
cell. For Flex-Core® honeycomb angles of 90 to 110° are preferred. The angles "e"
and "f' are chosen to ensure that tabs 62 and 60 fold so that the apices 63 and 61
fit within the junctions 40 and 42, respectively, at the sides of the cell.
[0025] The upper tab portion 66 includes a left upper lobe 66a and a right upper lobe 66b.
The lobes 66a and 66b are separated by a V-shaped notch 66c. The outer perimeters
70 and 72 of the lobes are preferably arcuate in shape as shown in FIG. 2. The combination
of arcuate perimeters 70 and 72 with the V-shaped notch 66c provides for particularly
effective folding and friction locking of the upper tab portion 66 within the concave
portion 38 of the cell wall.
[0026] The lower tab portion 64 includes a lower left lobe 64a and a lower right lobe 64b.
The lobes 64a and 64b are separated by a V-shaped notch 64c. The lower left lobe 64a
includes an outer end which has an angular perimeter with a centrally located apex.
The angular perimeter is formed by a first outwardly extending edge 74a and a second
outwardly extending edge 74b which are oriented at an angle (g) relative to each other
such that they meet at apex 75. The lower right lobe 64b also includes an outer end
which also has an angular perimeter with a centrally located apex. The angular perimeter
of the lower right lobe is formed by a first outwardly extending edge 76a and a second
outwardly extending edge 76b which are oriented at an angle (h) relative to each other
such that they meet at apex 77. The angles "g" and "h" are preferably approximately
equal (±5°) and may range from 100 to 160° depending upon the specific configuration
of the flexible honeycomb cell. For Flex-Core® honeycomb, angles of 120 to 140° are
preferred. Lower left and right lobes that have outer ends with angular perimeters
and centrally located apices, when combined with the V-shaped notch 64c, provide for
effective folding and friction locking of the lower tab portion 64 to the convex portion
32 of the cell wall.
[0027] In order to promote desired folding of the planar acoustic insert during insertion
into the cell and to provide the necessary friction locking of the insert to the cell
walls, it is preferred that tab portions are separated by V-shaped notches as shown
at 78, 80, 82 and 84. The V-notches extend inward and terminate relatively close to
the boundary 50 of the planar acoustic portion 48. The V-notches should not extend
across the boundary 50.
[0028] As shown in FIG. 7, the flexible acoustic honeycomb 10 is typically located between
a porous or perforated sound permeable face sheet 11 and a solid sound impermeable
acoustic barrier face sheet 13 to form an acoustic damping panel or structure which
is located near a source of noise 15, such as the interior of a jet engine. The solid
acoustic barrier face sheet 13 forms an acoustic barrier at the bottom of the acoustic
cells 18 that corresponds to the second edge 16 of the honeycomb 10. Each cell forms
an acoustic resonator that has a depth which is equal to the distance between the
first edge 14 and second edge 16. Individual acoustic barriers may be inserted into
the cells 18 when it is desired that the acoustic bottom of the cells does not correspond
to the second edge 16 of the honeycomb 10. The insertion of solid barriers into the
cells allows one to form acoustic resonators, when desired, that have depths that
are less than the distance between the first edge 14 and second edge 16 of the honeycomb
10.
[0029] As also shown in FIG. 7, the tab portions are preferably folded during insertion
so that all of the tab portions are on the side of the septum portion which is closest
to the noise source. This provides anchoring of the septum to the honeycomb walls
on the side of the septum portion that is located nearest to the first edge of the
honeycomb and the noise source. However, in some situations, it may be desirable to
orient the septum portions within the cell so that the tab portions are located nearest
to the second edge and away from the noise source.
[0030] The planar acoustic septum 46 is inserted into the honeycomb cell 18 using an insertion
tool or plunger. A separate forming die may be used to provide initial folding of
the planar acoustic septum prior to insertion into the honeycomb cell. However, a
pre-forming die is not usually required or used. Typically, the first edge 14 of the
honeycomb functions as the forming die during insertion of the planar acoustic septum.
Single planar acoustic septum may be inserted using a single plunger or multiple septa
may be simultaneously inserted using multiple plungers.
[0031] The cross-sectional shape of the plunger, as well as the cross-sectional size relative
to the planar acoustic septum and cell cross-sectional sizes, must be taken into consideration
to ensure proper folding and friction-locking. A preferred plunger design is shown
at 90 in FIG. 5. The plunger 90 includes a plunger body 92 and a plunger face 94 that
contacts the planar acoustic septum. The plunger face 94 preferably has a cross-sectional
shape as shown in FIG.5.
[0032] Although other cross-sectional shapes are possible, the cross-sectional shape shown
in FIG. 5 was found to provide desired folding of the planar acoustic septum during
insertion into the honeycomb to provide a desired planar portion 48 that is securely
friction-locked in the cell. The preferred plunger face has a convex portion 96 and
a concave portion 98. The convex portion includes a centrally located apex 100. During
septum insertion, the apex 100 is located adjacent to the concave portion 38 of the
cell and the concave portion 98 of the plunger is located adjacent to the convex portion
32 of the cell. The cross-sectional size of the plunger face 94 is chosen depending
upon the thickness of the septum material, the inherent spring back of the septum
material and the size and shape of the cell opening.
[0033] FIG. 6 shows a simplified side-sectional view of septum caps 44P, which have been
formed from planar acoustic septum inserts 46, and which have been pressed into place
within flexible honeycomb 10P using plunger 90. The identifying numbers in FIG. 6
correspond to the numbers in FIG. 1 and 2, except that a P is added to indicate that
the honeycomb is a precursor structure that still requires permanent bonding of the
septum caps 44P in order to form the flexible acoustic honeycomb 10. The septum caps
44P are friction-locked in place by the inherent bounce back of the acoustic insert
material. The insertion process places the planar septum portion 48P so that it extends
transverse (90° ± 10°) to the cell walls at the desired insertion depth. The tab portions
are shown in their folded positions at 51.
[0034] The flexible honeycomb 10P is dipped into a pool of adhesive 110 so that the tab
portions are immersed in the adhesive. The flexible honeycomb 10P is removed from
the adhesive pool 110 and the liquid adhesive is dried or cured to form the flexible
acoustic honeycomb 10. This type of adhesive application procedure provides for permanent
bonding of the septum caps 44 within the flexible acoustic honeycomb 10. Once formed,
the flexible acoustic honeycomb may be used to form a wide variety of curved structures
having tight radii of curvature and/or compound curves.
[0035] Any of the liquid adhesives typically used to bond septum caps to honeycomb walls
may be used to bond the septum caps to the flexible honeycomb walls. Preferred adhesives
include those that are stable at high temperature (150 - 200°C). Exemplary adhesives
include epoxies, acrylics, phenolics, cyanoacrylates, bismaleimides, polyamide-imides,
and polyimides. Polyamide-imide adhesives are preferred. The adhesives are chosen
to be compatible with both the septum material and the honeycomb material.
[0036] The materials used to make the flexible honeycomb 10 can be any of those typically
used to make flexible honeycomb, such as metals and composite materials. Exemplary
metals include aluminum and aluminum alloys. Exemplary composite materials include
fiberglass, resin impregnated aramid paper, such as Nomex®, and various combinations
of graphite fibers with suitable matrix resins. Matrix resins that can withstand relatively
high temperatures (150 to 200°C) are preferred.
[0037] The materials used to make the solid acoustic barrier face sheets 13 can be any of
the solid face sheet materials commonly used for acoustic structures which typically
include the same type of materials used to make the honeycomb structure. The materials
used to make the perforated sound permeable face sheet 11 can also be any of the materials
commonly used for such porous structures provided that the pores or perforations in
the structure are sufficient to allow the sound waves from the jet engine or other
noise source to enter into the acoustic cells or resonators. The face sheet materials
should be sufficiently flexible to allow bonding of the face sheets to the flexible
honeycomb once it has been formed into the desired curved structure.
[0038] The flexible honeycomb used to make the acoustic honeycomb can be any flexible honeycomb
having the type of cells which are shaped to provide the combination of convex and
concave curvatures as set forth previously. A preferred flexible honeycomb is Flex-Core®
flexible honeycomb which is available from Hexcel Corporation (Dublin, California).
The flexible honeycomb shown in FIG. 1 is representative of Flex-Core® flexible honeycomb.
Flex-Core® flexible honeycomb is made from a variety of suitable materials including
5052 or 5056 aluminum, aramid/phenolic composite and fiberglass/phenolic composite.
[0039] The flexible honeycomb cells used for making flexible acoustic honeycomb will typically
have a cross-sectional area ranging from 32.26 mm
2 (0.05 square inch) to 645.2 mm
2 (1 square inch) or more. The depth of the acoustic cells (honeycomb or core thickness
T) will generally range from 6.35 mm to 76.2 mm (0.25 to 3 inches) or more. The wall
thicknesses of the honeycomb material will typically range from 0.025 mm to 1.27 mm
(0.001 to 0.050 inch). For jet engine nacelles, the flexible honeycomb cells will
typically have a cross-sectional area of about 64.5 to 322.6 mm
2 (0.1 to 0.5 square inch), wall thicknesses of around 0.635 mm to 1.27 mm (0.025 to
0.05 inch) and a depth of about 25.4 to 50.8 mm (1.0 and 2.0 inches).
[0040] Any of the standard acoustic materials may be used to form the septum caps 44. These
acoustic materials are typically provided as relatively thin sheets that are perforated,
porous or an open mesh fabric that is designed to provide noise attenuation. Perforations
are formed in the solid sheet material either before or after the septa are placed
within the flexible honeycomb cells. Although any suitable metal, ceramic or plastic
acoustic material may be used to make perforated septa, it is preferred that the acoustic
material be polyether ether ketone (PEEK) or a similar chemically resistant polymer
material that is suitable for high temperature applications. Sheets or films of PEEK
are available commercially from a number of sources, such as Victrex USA (Greenville,
South Carolina) which produces sheets of PEEK under the tradename VICTREX® PEEK™ polymer.
[0041] When using solid films as the septum material, holes are drilled through the film
within the overall boundary 50 of the planar acoustic portion 48. The holes may be
drilled using a laser or other suitable hole drilling system. The various tab portions
that are located outside the overall boundary 50 may remain solid or can also be drilled
to varying degrees, if desired, to increase surface area and adhesive bonding of the
tab portions to the cell walls.
[0042] Although perforated and porous sheets of various materials (metals, ceramics, plastics)
may be used, it is preferred that the acoustic material be an open mesh fabric that
is woven from monofilament fibers. The fibers may be composed of glass, carbon, ceramic
or polymers. Monofilament polymer fibers made from polyamide, polyester, polyethylene
chlorotrifluoroethylene (ECTFE), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene
(PTFE), polyphenylene sulfide (PPS), polyfluoroethylene propylene (FEP), poly ether
ether ketone (PEEK), polyamide 6 (Nylon, 6 PA6) and polyamide 12 (Nylon 12, PA12);
are just a few examples. Open mesh monofilament fabric made from PEEK is preferred
for high temperature applications. Open mesh monofilament acoustic fabrics and other
acoustic materials that may be used to form the septum caps in accordance with the
present invention are available from a wide variety of commercial sources. For example,
sheets of open mesh monofilament acoustic fabric may be obtained from SEFAR America
Inc. (Buffalo Division Headquarters 111 Calumet Street Depew, NY 14043) under the
trade names SEFAR PETEX, SEFAR NITEX and SEFAR PEEKTEX.
[0043] Hybrid septum caps are possible where the planar septum portion is made from an open
mesh monofilament fabric with tab portions being made from solid films of plastic.
In certain situations, this combination may provide desired acoustic properties and
septum strength. For example, a PEEK open mesh fabric planar septum portion combined
with tab portions that are PEEK solid film is possible. The PEEK open mesh fabric
is heat bonded or welded to the solid film tab portions in accordance with known thermal
bonding procedures. The solid film tab portions may be perforated, if desired to aid
in adhesive bonding of the tab portions to the cell walls.
[0044] Although the acoustic fabric can be made from a combination of different woven fibers,
it is preferred that the fibers in the acoustic fabric be made from the same material.
In many acoustic fabrics the warp direction fibers (warp fibers) are generally made
from smaller diameter fibers than the weft direction fibers (weft fibers). Accordingly,
the weft fibers tend to be stronger and less flexible than the warp direction fibers.
Flexibility of the weft fibers may also be increased relative to the warp fibers by
altering the chemistry (rather than the diameter) of the weft fiber to provide a stiffer
fiber.
[0045] In woven fabric where the fibers in one direction are less flexible or stronger than
the cross-direction fibers, the stronger fibers are commonly referred to as the dominant
fibers. The planar acoustic septum inserts may be made from all types of woven acoustic
fabric including those where there is no dominant fiber. However, it is preferred
that the woven monofilament acoustic septum material includes dominate fibers and
that the dominate fibers are the weft fibers.
[0046] A preferred planar acoustic septum insert for use in the present invention is shown
at 120 in FIG. 3. The planar acoustic septum insert is a woven monofilament open mesh
acoustic fabric in which dominate weft fibers 122 are oriented parallel to each other
and extend in a direction from the lower tab portion 124 to the upper tab portion
126. The warp fibers 128 are oriented parallel to each other and extend in a direction
between the apices 130 and 132 of the outer ends of the left and right tab portions.
It was discovered that orienting the weft (dominate) fibers and warp fibers, as shown
in FIG. 3, provides for folding and friction-locking of the planar acoustic septum
insert to the honeycomb cell walls that is more effective than other dominate fiber
orientations.
[0047] Preferred weft fiber orientations include those where the weft fiber extend in a
direction that is substantially perpendicular to line 140, as shown in FIG. 3. Line
140 is preferably parallel to the outwardly extending edges 140a and 140b of the lower
tab portion 124. Line 140 would also be parallel to the outwardly extending edges
74b and 76a of the lower tab portion 64 of the planar acoustic insert shown in FIG.
2. Substantially perpendicular means that the angle between the weft fiber direction
and line 140 may vary from 80 to 100 degrees. Line 140 is also preferably parallel
to a line extending from the apex 130 to apex 132.
[0048] An alternate preferred planar acoustic septum insert for use in the present invention
is one where the dominate weft fibers are oriented parallel to each other and extend
in a direction between the apices of the outer ends of the left and right tab portions.
The warp fibers are oriented parallel to each other and extend in a direction from
the lower tab portion to the upper tab portion. This orientation of the dominate weft
fibers also provides for folding and friction-locking of the planar acoustic septum
insert to the honeycomb cell walls that is more effective than other dominate fiber
orientations. In addition, the V-shaped notch 66c may be eliminated when this orientation
of dominate fibers is utilized. The alternate preferred planar acoustic septum insert
includes dominate weft fiber orientations where the weft fibers extend in a direction
that is substantially parallel to line 140. Substantially parallel means that the
angle between the weft fiber direction and line 140 may vary from +10 to -10 degrees.
1. An acoustic structure (10) in which acoustic septa (44) are located in the cells (18)
of a honeycomb (12) for reducing the noise generated from a source (15), said acoustic
structure (10) comprising:
A) a honeycomb (12) comprising a first edge (14) to be located closest to said source
(15) and a second edge (16), said honeycomb (12) comprising a cell (18) having a left
side (20) and a right side (22), said cell (18) being defined by a lower wall (24)
that extends between said first and second edges (14, 16) and an upper wall (26) that
also extends between said first and second edges (14, 16), said lower wall (24) comprising
a lower left end portion (28), a lower right end portion (30) and a convex portion
(32) located between said lower left and lower right end portions (28, 30), said upper
wall (26) comprising an upper left end portion (34), an upper right end portion (36)
and a concave portion (38) located between said upper left and upper right end portions
(34, 36), wherein said lower left end portion (28) and said upper left end portion
(34) are connected to form a left junction (40) along the left side (20) of said cell
(18) and said lower right end portion (30) and said upper right end portion (36) are
connected to form a right junction (42) along the right side (22) of said cell (18);
the structure characterised by
B) an acoustic septum (44) comprising:
a) a planar acoustic portion (48) extending transverse to said upper and lower walls
(26, 24), said planar acoustic portion (48) having a top side located nearest to said
first edge (14), a bottom side located nearest to said second edge (16), a right boundary
(52), a left boundary (54), a lower boundary (56) and an upper boundary (58);
b) a right tab portion (60) protruding from said acoustic portion (48) at said right
boundary (52);
c) a left tab portion (62) protruding from said acoustic portion (48) at said left
boundary (54);
d) a lower tab portion (64) protruding from said acoustic portion (48) at said lower
boundary (56);
e) an upper tab portion (66) protruding from said acoustic portion (48) at said upper
boundary (58); and
C) an adhesive (110) that bonds said right tab portion (60), left tab portion (62),
lower tab portion (64) and upper tab portion (66) to said honeycomb (12) wherein said
right tab portion (60) is bonded to said lower right end portion (30) and said upper
right end portion (36), said left tab portion (62) is bonded to said lower left end
portion (28) and said upper left end portion (34), said lower tab portion (64) is
bonded to said convex portion (32) and said upper tab portion (66) is bonded to said
concave portion (38).
2. An acoustic structure (10) according to claim 1 wherein said upper tab portion (66)
comprises a left upper lobe (66a) and a right upper lobe (66b) and said lower tab
portion (64) comprises a left lower lobe (64a) and a right lower lobe (64b); optionally:
wherein said left lower lobe (64a) is separated from said right lower lobe (64b) by
a V-shaped notch (64c), or
wherein said left upper lobe (66a) and said right upper lobe (66b) each have a curved
perimeter (70, 72), or
wherein said left lower lobe (64a) and said right lower lobe (64b) each have an outer
end formed by an angular perimeter (74a, 74b; 76a, 76b) with a centrally located apex
(75, 77).
3. An acoustic structure (10) according to claim 1 wherein V-shaped notches (78, 80)
separate the upper tab portion (66) from said right tab portion (60) and said left
tab portion (62).
4. An acoustic structure (10) according to claim 1 wherein said right tab portion (60)
and said left tab portion (62) each have an outer end formed by an angular perimeter
(60a, 60b; 62a, 62b) with a centrally located apex (61, 63).
5. An acoustic structure (10) according to claim 1 wherein said acoustic septum (120)
is an acoustic mesh comprising dominate monofilament fibers (122) which extend parallel
to each other in a direction from said lower tab portion (124) to said upper tab portion
(126); or wherein said acoustic septum (120) is an acoustic mesh comprising dominate
monofilament fibers (130) which extend parallel to each other in a direction from
said left tab portion (62) to said right tab portion (60).
6. An acoustic structure (10) according to claim 1 which includes a sound permeable sheet
(11) attached to the first edge (14) of said honeycomb (12) and a solid sound impermeable
sheet (13) attached to the second edge (16) of said honeycomb (12).
7. A method for making an acoustic structure (10) in which acoustic septa (44) are located
in the cells (18) of a honeycomb (12) for reducing the noise generated from a source
(15), said method comprising the steps of:
A) providing a flexible honeycomb (12) comprising a first edge (14) to be located
closest to said source (15) and a second edge (16), said flexible honeycomb (12) comprising
a cell (18) having a left side (20) and a right side (22), said cell (18) being defined
by a lower wall (24) that extends between said first and second edges (14, 16) and
an upper wall (26) that also extends between said first and second edges (14, 16),
said lower wall (24) comprising a lower left end portion (28), a lower right end portion
(30) and a convex portion (32) located between said lower left and lower right end
portions (28, 30), said upper wall (26) comprising an upper left end portion (34),
an upper right end portion (36) and a concave portion (38) located between said upper
left and upper right end portions (34, 36), wherein said lower left end portion (28)
and said upper left end portion (34) are connected to form a left junction (40) along
the left side (20) of said cell (18) and said lower right end portion (30) and said
upper right end portion (36) are connected to form a right junction (42) along the
right side (22) of said cell (18); the method characterised by
B) providing a planar acoustic septum insert (46) comprising:
a) a planar acoustic portion (48) having a right boundary (52), a left boundary (54),
a lower boundary (56) and an upper boundary (58);
b) a right tab portion (60) protruding from said acoustic portion (48) at said right
boundary (52);
c) a left tab portion (62) protruding from said acoustic portion (48) at said left
boundary (54);
d) a lower tab portion (64) protruding from said acoustic portion (48) at said lower
boundary (56); and
e) an upper tab portion (66) protruding from said acoustic portion (48) at said upper
boundary (58);
C) inserting said planar acoustic septum insert (46) into said cell (18) to form an
acoustic septum (44) wherein said planar acoustic portion (48) extends transverse
to said upper and lower walls (26, 24), said planar acoustic portion (48) having a
top side located nearest to said first edge (14), a bottom side located nearest to
said second edge (16); and
D) bonding said right tab portion (60), left tab portion (62), lower tab portion (64)
and upper tab portion (66) to said honeycomb (12) wherein said right tab portion (60)
is bonded to said lower right end portion (30) and said upper right end portion (36),
said left tab portion (62) is bonded to said lower left end portion (28) and said
upper left end portion (34), said lower tab portion (64) is bonded to said convex
portion (32) and said upper tab portion (66) is bonded to said concave portion (38).
8. A method for making an acoustic structure (10) according to claim 7 wherein said upper
tab portion (66) comprises a left upper lobe (66a) and a right upper lobe (66b) and
said lower tab portion (64) comprises a left lower lobe (64a) and a right lower lobe
(64b); optionally wherein said left lower lobe (64a) is separated from said right
lower lobe (64b) by a V-shaped notch (64c), or
wherein said left upper lobe (66a) and said right upper lobe (66b) each have a curved
perimeter (70, 72), or
wherein said left lower lobe (64a) and said right lower lobe (64b) each have an angular
perimeter (74a, 74b; 76a, 76b) with a centrally located apex (75, 77).
9. A method for making an acoustic structure (10) according to claim 7 wherein V-shaped
notches (78, 80) separate the upper tab portion (66) from said right tab portion (60)
and said left tab portion (62).
10. A method for making an acoustic structure (10) according to claim 7 wherein said right
tab portion (60) and said left tab portion (62) each have an outer end formed by an
angular perimeter (60a, 60b; 62a, 62b) with a centrally located apex (61, 63).
11. A method for making an acoustic (10) structure according to claim 7 wherein said acoustic
septum (120) is an acoustic mesh comprising dominate monofilament fibers (122) which
extend parallel to each other in a direction from said lower tab portion (124) to
said upper tab portion (126), or wherein said acoustic septum (120) is an acoustic
mesh comprising dominate monofilament fibers (130) which extend parallel to each other
in a direction from said left tab portion (130) to said right tab portion (132).
12. A method for making an acoustic structure (10) according to claim 7 which includes
the steps of attaching a sound permeable sheet (11) to the first edge (14) of said
honeycomb (12) and attaching a solid sound impermeable sheet (13) to the second edge
(16) of said honeycomb (12).
1. Akustische Struktur (10), in der sich akustische Septen (44) in den Zellen (18) einer
Wabe (12) befinden, um das Geräusch zu reduzieren, das von einer Quelle (15) erzeugt
wird, wobei die akustische Struktur (10) Folgendes umfasst:
A) eine Wabe (12), umfassend eine erste Kante (14), die sich am nächsten zu der Quelle
(15) befinden soll, und eine zweite Kante (16), wobei die Wabe (12) eine Zelle (18)
umfasst, die eine linke Seite (20) und eine rechte Seite (22) aufweist, wobei die
Zelle (18) durch eine untere Wand (24), die sich zwischen der ersten und der zweiten
Kante (14, 16) erstreckt, und eine obere Wand (26) definiert ist, die sich ebenfalls
zwischen der ersten und der zweiten Kante (14, 16) erstreckt, wobei die untere Wand
(24) einen unteren linken Endabschnitt (28), einen unteren rechten Endabschnitt (30)
und einen konvexen Abschnitt (32) umfasst, der sich zwischen dem unteren linken und
dem unteren rechten Endabschnitt (28, 30) befindet, wobei die obere Wand (26) einen
oberen linken Endabschnitt (34), einen oberen rechten Endabschnitt (36) und einen
konkaven Abschnitt (38) umfasst, der sich zwischen dem oberen linken und dem oberen
rechten Endabschnitt (34, 36) befindet, wobei der untere linke Endabschnitt (28) und
der obere linke Endabschnitt (34) verbunden sind, um einen linken Anschluss (40) entlang
der linken Seite (20) der Zelle (18) zu bilden und der untere rechte Endabschnitt
(30) und der obere rechte Endabschnitt (36) verbunden sind, um einen rechten Anschluss
(42) entlang der rechten Seite (22) der Zelle (18) zu bilden; wobei die Struktur durch
Folgendes gekennzeichnet ist:
B) ein akustisches Septum (44), umfassend:
a) einen planaren akustischen Abschnitt (48), der sich quer zu der oberen und der
unteren Wand (26, 24) erstreckt, wobei der planare akustische Abschnitt (48) eine
obere Seite, die sich am nächsten zu der ersten Kante (14) befindet, eine untere Seite,
die sich am nächsten zu der zweiten Kante (16) befindet, eine rechte Grenze (52),
eine linke Grenze (54), eine untere Grenze (56) und eine obere Grenze (58) aufweist;
b) einen rechten Laschenabschnitt (60), der von dem akustischen Abschnitt (48) an
der rechten Grenze (52) vorsteht;
c) einen linken Laschenabschnitt (62), der von dem akustischen Abschnitt (48) an der
linken Grenze (54) vorsteht;
d) einen unteren Laschenabschnitt (64), der von dem akustischen Abschnitt (48) an
der unteren Grenze (56) vorsteht;
e) einen oberen Laschenabschnitt (66), der von dem akustischen Abschnitt (48) an der
oberen Grenze (58) vorsteht; und
C) einen Klebstoff (110), der den rechten Laschenabschnitt (60), den linken Laschenabschnitt
(62), den unteren Laschenabschnitt (64) und den oberen Laschenabschnitt (66) an die
Wabe (12) bindet, wobei der rechte Laschenabschnitt (60) an den unteren rechten Endabschnitt
(30) und den oberen rechten Endabschnitt (36) gebunden ist, der linke Laschenabschnitt
(62) an den unteren linken Endabschnitt (28) und den oberen linken Endabschnitt (34)
gebunden ist, der untere Laschenabschnitt (64) an den konvexen Abschnitt (32) gebunden
ist und der obere Laschenabschnitt (66) an den konkaven Abschnitt (38) gebunden ist.
2. Akustische Struktur (10) nach Anspruch 1, wobei der obere Laschenabschnitt (66) einen
linken oberen Lappen (66a) und einen rechten oberen Lappen (66b) umfasst und der untere
Laschenabschnitt (64) einen linken unteren Lappen (64a) und einen rechten unteren
Lappen (64b) umfasst; optional:
wobei der linke untere Lappen (64a) von dem rechten unteren Lappen (64b) durch eine
V-förmige Kerbe (64c) getrennt ist, oder
wobei der linke obere Lappen (66a) und der rechte obere Lappen (66b) jeweils einen
gekrümmten Umfang (70, 72) aufweisen, oder
wobei der linke untere Lappen (64a) und der rechte untere Lappen (64b) jeweils ein
äußeres Ende aufweisen, das durch einen Winkelumfang (74a, 74b; 76a, 76b) mit einer
sich zentral befindenden Spitze (75, 77) gebildet ist.
3. Akustische Struktur (10) nach Anspruch 1, wobei V-förmige Kerben (78, 80) den oberen
Laschenabschnitt (66) von dem rechten Laschenabschnitt (60) und dem linken Laschenabschnitt
(62) trennen.
4. Akustische Struktur (10) nach Anspruch 1, wobei der rechte Laschenabschnitt (60) und
der linke Laschenabschnitt (62) jeweils ein äußeres Ende aufweisen, das durch einen
Winkelumfang (60a, 60b; 62a, 62b) mit einer sich zentral befindenden Spitze (61, 63)
gebildet ist.
5. Akustische Struktur (10) nach Anspruch 1, wobei das akustische Septum (120) ein akustisches
Netz ist, das dominierende Monofilamentfasern (122) umfasst, die sich parallel zueinander
in einer Richtung von dem unteren Laschenabschnitt (124) zu dem oberen Laschenabschnitt
(126) erstrecken; oder wobei das akustische Septum (120) ein akustisches Netz ist,
das dominierende Monofilamentfasern (130) umfasst, die sich parallel zueinander in
einer Richtung von dem linken Laschenabschnitt (62) zu dem rechten Laschenabschnitt
(60) erstrecken.
6. Akustische Struktur (10) nach Anspruch 1, die eine schalldurchlässige Lage (11), die
an der ersten Kante (14) der Wabe (12) angebracht ist, und eine feste schallundurchlässige
Lage (13) beinhaltet, die an der zweiten Kante (16) der Wabe (12) angebracht ist.
7. Verfahren zum Herstellen einer akustischen Struktur (10), bei der sich akustische
Septen (44) in den Zellen (18) einer Wabe (12) befinden, um das Geräusch zu reduzieren,
das von einer Quelle (15) erzeugt wird, wobei das Verfahren die folgenden Schritte
umfasst:
A) Bereitstellen einer flexiblen Wabe (12), umfassend eine erste Kante (14), die sich
am nächsten zu der Quelle (15) befinden soll, und eine zweite Kante (16), wobei die
flexible Wabe (12) eine Zelle (18) umfasst, die eine linke Seite (20) und eine rechte
Seite (22) aufweist, wobei die Zelle (18) durch eine untere Wand (24), die sich zwischen
der ersten und der zweiten Kante (14, 16) erstreckt, und eine obere Wand (26) definiert
ist, die sich ebenfalls zwischen der ersten und der zweiten Kante (14, 16) erstreckt,
wobei die untere Wand (24) einen unteren linken Endabschnitt (28), einen unteren rechten
Endabschnitt (30) und einen konvexen Abschnitt (32) umfasst, der sich zwischen dem
unteren linken und dem unteren rechten Endabschnitt (28, 30) befindet, wobei die obere
Wand (26) einen oberen linken Endabschnitt (34), einen oberen rechten Endabschnitt
(36) und einen konkaven Abschnitt (38) umfasst, der sich zwischen dem oberen linken
und dem oberen rechten Endabschnitt (34, 36) befindet, wobei der untere linke Endabschnitt
(28) und der obere linke Endabschnitt (34) verbunden sind, um einen linken Anschluss
(40) entlang der linken Seite (20) der Zelle (18) zu bilden und der untere rechte
Endabschnitt (30) und der obere rechte Endabschnitt (36) verbunden sind, um einen
rechten Anschluss (42) entlang der rechten Seite (22) der Zelle (18) zu bilden; wobei
das Verfahren durch Folgendes gekennzeichnet ist:
B) Bereitstellen eines planaren akustischen Septumeinsatzes (46), umfassend:
a) einen planaren akustischen Abschnitt (48), der eine rechte Grenze (52), eine linke
Grenze (54), eine untere Grenze (56) und eine obere Grenze (58) aufweist;
b) einen rechten Laschenabschnitt (60), der von dem akustischen Abschnitt (48) an
der rechten Grenze (52) vorsteht;
c) einen linken Laschenabschnitt (62), der von dem akustischen Abschnitt (48) an der
linken Grenze (54) vorsteht;
d) einen unteren Laschenabschnitt (64), der von dem akustischen Abschnitt (48) an
der unteren Grenze (56) vorsteht; und
e) einen oberen Laschenabschnitt (66), der von dem akustischen Abschnitt (48) an der
oberen Grenze (58) vorsteht;
C) Einsetzen des planaren akustischen Septumeinsatzes (46) in die Zelle (18), um ein
akustisches Septum (44) zu bilden, wobei sich der planare akustische Abschnitt (48)
quer zu der oberen und der unteren Wand (26, 24) erstreckt, wobei der planare akustische
Abschnitt (48) eine obere Seite aufweist, die sich am nächsten zu der ersten Kante
(14) befindet, eine untere Seite, die sich am nächsten zu der zweiten Kante (16) befindet;
und
D) Binden des rechten Laschenabschnittes (60), des linken Laschenabschnittes (62),
des unteren Laschenabschnittes (64) und des oberen Laschenabschnittes (66) an die
Wabe (12), wobei der rechte Laschenabschnitt (60) an den unteren rechten Endabschnitt
(30) und den oberen rechten Endabschnitt (36) gebunden ist, der linke Laschenabschnitt
(62) an den unteren linken Endabschnitt (28) und den oberen linken Endabschnitt (34)
gebunden ist, der untere Laschenabschnitt (64) an den konvexen Abschnitt (32) gebunden
ist und der obere Laschenabschnitt (66) an den konkaven Abschnitt (38) gebunden ist.
8. Verfahren zum Herstellen einer akustischen Struktur (10) nach Anspruch 7, wobei der
obere Laschenabschnitt (66) einen linken oberen Lappen (66a) und einen rechten oberen
Lappen (66b) umfasst und der untere Laschenabschnitt (64) einen linken unteren Lappen
(64a) und einen rechten unteren Lappen (64b) umfasst; wobei optional der linke untere
Lappen (64a) von dem rechten unteren Lappen (64b) durch eine V-förmige Kerbe (64c)
getrennt ist, oder
wobei der linke obere Lappen (66a) und der rechte obere Lappen (66b) jeweils einen
gekrümmten Umfang (70, 72) aufweisen, oder
wobei der linke untere Lappen (64a) und der rechte untere Lappen (64b) jeweils einen
Winkelumfang (74a, 74b; 76a, 76b) mit einer sich zentral befindenden Spitze (75, 77)
aufweisen.
9. Verfahren zum Herstellen einer akustischen Struktur (10) nach Anspruch 7, wobei V-förmige
Kerben (78, 80) den oberen Laschenabschnitt (66) von dem rechten Laschenabschnitt
(60) und dem linken Laschenabschnitt (62) trennen.
10. Verfahren zum Herstellen einer akustischen Struktur (10) nach Anspruch 7, wobei der
rechte Laschenabschnitt (60) und der linke Laschenabschnitt (62) jeweils ein äußeres
Ende aufweisen, das durch einen Winkelumfang (60a, 60b; 62a, 62b) mit einer sich zentral
befindenden Spitze (61, 63) gebildet ist.
11. Verfahren zum Herstellen einer akustischen (10) Struktur nach Anspruch 7, wobei das
akustische Septum (120) ein akustisches Netz ist, das dominierende Monofilamentfasern
(122) umfasst, die sich parallel zueinander in einer Richtung von dem unteren Laschenabschnitt
(124) zu dem oberen Laschenabschnitt (126) erstrecken, oder wobei das akustische Septum
(120) ein akustisches Netz ist, das dominierende Monofilamentfasern (130) umfasst,
die sich parallel zueinander in einer Richtung von dem linken Laschenabschnitt (130)
zu dem rechten Laschenabschnitt (132) erstrecken.
12. Verfahren zum Herstellen einer akustischen Struktur (10) nach Anspruch 7, das die
Schritte des Anbringens einer schalldurchlässigen Lage (11) an der ersten Kante (14)
der Wabe (12) und des Anbringens einer festen schallundurchlässigen Lage (13) an der
zweiten Kante (16) der Wabe (12) beinhaltet.
1. Structure acoustique (10) dans laquelle des cloisons acoustiques (44) sont situées
dans les alvéoles (18) d'un nid d'abeilles (12) en vue de la réduction du bruit généré
à partir d'une source (15), ladite structure acoustique (10) comprenant :
A) un nid d'abeilles (12) comprenant un premier bord (14) à placer au plus près de
ladite source (15) et un second bord (16), ledit nid d'abeilles (12) comprenant une
alvéole (18) possédant un côté gauche (20) et un côté droit (22), ladite alvéole (18)
étant définie par une paroi inférieure (24) qui s'étend entre lesdits premier et second
bords (14, 16) et une paroi supérieure (26) qui s'étend également entre lesdits premier
et second bords (14, 16), ladite paroi inférieure (24) comprenant une partie d'extrémité
inférieure gauche (28), une partie d'extrémité inférieure droite (30) et une partie
convexe (32) située entre lesdites parties d'extrémité inférieure gauche et inférieure
droite (28, 30), ladite paroi supérieure (26) comprenant une partie d'extrémité supérieure
gauche (34), une partie d'extrémité supérieure droite (36) et une partie concave (38)
située entre lesdites parties d'extrémité supérieure gauche et supérieure droite (34,
36), ladite partie d'extrémité inférieure gauche (28) et ladite partie d'extrémité
supérieure gauche (34) étant raccordées pour former une jonction gauche (40) le long
du côté gauche (20) de ladite alvéole (18) et ladite partie d'extrémité inférieure
droite (30) et ladite partie d'extrémité supérieure droite (36) étant raccordées pour
former une jonction droite (42) le long du côté droit (22) de ladite alvéole (18)
; la structure étant caractérisée par
B) une cloison acoustique (44) comprenant :
a) une partie acoustique plane (48) s'étendant transversalement auxdites parois supérieure
et inférieure (26, 24), ladite partie acoustique plane (48) possédant un côté supérieur
situé le plus proche dudit premier bord (14), un côté inférieur situé le plus proche
dudit second bord (16), une limite droite (52), une limite gauche (54), une limite
inférieure (56) et une limite supérieure (58) ;
b) une partie languette droite (60) faisant saillie à partir de ladite partie acoustique
(48) au niveau de ladite limite droite (52) ;
c) une partie languette gauche (62) faisant saillie à partir de ladite partie acoustique
(48) au niveau de ladite limite gauche (54);
d) une partie languette inférieure (64) faisant saillie à partir de ladite partie
acoustique (48) au niveau de ladite limite inférieure (56);
e) une partie languette supérieure (66) faisant saillie à partir de ladite partie
acoustique (48) au niveau de ladite limite supérieure (58) ; et
C) un adhésif (110) qui lie ladite partie languette droite (60), ladite partie languette
gauche (62), ladite partie languette inférieure (64) et ladite partie languette supérieure
(66) audit nid d'abeilles (12), ladite partie languette droite (60) étant liée à ladite
partie d'extrémité inférieure droite (30) et à ladite partie d'extrémité supérieure
droite (36), ladite partie languette gauche (62) étant liée à ladite partie d'extrémité
inférieure gauche (28) et à ladite partie d'extrémité supérieure gauche (34), ladite
partie languette inférieure (64) étant liée à ladite partie convexe (32) et ladite
partie languette supérieure (66) étant liée à ladite partie concave (38).
2. Structure acoustique (10) selon la revendication 1, ladite partie languette supérieure
(66) comprenant un lobe supérieur gauche (66a) et un lobe supérieur droit (66b) et
ladite partie languette inférieure (64) comprenant un lobe inférieur gauche (64a)
et un lobe inférieur droit (64b) ; éventuellement :
ledit lobe inférieur gauche (64a) étant séparé dudit lobe inférieur droit (64b) par
une entaille en forme de V (64c), ou
ledit lobe supérieur gauche (66a) et ledit lobe supérieur droit (66b) présentant chacun
un périmètre incurvé (70, 72), ou
ledit lobe inférieur gauche (64a) et ledit lobe inférieur droit (64b) comportant chacun
une extrémité externe formée par un périmètre angulaire (74a, 74b ; 76a, 76b) avec
un sommet situé au centre (75, 77).
3. Structure acoustique (10) selon la revendication 1, des entailles en forme de V (78,
80) séparant la partie languette supérieure (66) de ladite partie languette droite
(60) et de ladite partie languette gauche (62).
4. Structure acoustique (10) selon la revendication 1, ladite partie languette droite
(60) et ladite partie languette gauche (62) possédant chacune une extrémité externe
formée par un périmètre angulaire (60a, 60b ; 62a, 62b) avec un sommet situé au centre
(61, 63).
5. Structure acoustique (10) selon la revendication 1, ladite cloison acoustique (120)
étant un maillage acoustique comprenant des fibres monofilaments dominantes (122)
qui s'étendent parallèlement les unes aux autres dans une direction allant de ladite
partie languette inférieure (124) à ladite partie languette supérieure (126) ; ou
ladite cloison acoustique (120) étant un maillage acoustique comprenant des fibres
monofilaments dominantes (130) qui s'étendent parallèlement les unes aux autres dans
une direction allant de ladite partie languette gauche (62) à ladite partie languette
droite (60).
6. Structure acoustique (10) selon la revendication 1, qui comprend une feuille perméable
au son (11) fixée au premier bord (14) dudit nid d'abeilles (12) et une feuille solide
imperméable au son (13) fixée au second bord (16) dudit nid d'abeilles (12).
7. Procédé permettant la fabrication d'une structure acoustique (10) dans laquelle des
cloisons acoustiques (44) sont situées dans les alvéoles (18) d'un nid d'abeilles
(12) en vue de la réduction du bruit généré à partir d'une source (15), ledit procédé
comprenant les étapes de :
A) fourniture d'un nid d'abeilles souple (12) comprenant un premier bord (14) à placer
le plus proche de ladite source (15) et un second bord (16), ledit nid d'abeilles
souple (12) comprenant une alvéole (18) possédant un côté gauche (20) et un côté droit
(22), ladite alvéole (18) étant définie par une paroi inférieure (24) qui s'étend
entre lesdits premier et second bords (14, 16) et une paroi supérieure (26) qui s'étend
également entre lesdits premier et second bords (14, 16), ladite paroi inférieure
(24) comprenant une partie d'extrémité inférieure gauche (28), une partie d'extrémité
inférieure droite (30) et une partie convexe (32) située entre lesdites parties d'extrémité
inférieure gauche et inférieure droite (28, 30), ladite paroi supérieure (26) comprenant
une partie d'extrémité supérieure gauche (34), une partie d'extrémité supérieure droite
(36) et une partie concave (38) située entre lesdites parties d'extrémité supérieure
gauche et supérieure droite (34, 36), ladite partie d'extrémité inférieure gauche
(28) et ladite partie d'extrémité supérieure gauche (34) étant raccordées pour former
une jonction gauche (40) le long du côté gauche (20) de ladite alvéole (18) et ladite
partie d'extrémité inférieure droite (30) et ladite partie d'extrémité supérieure
droite (36) étant raccordées pour former une jonction droite (42) le long du côté
droit (22) de ladite alvéole (18) ; le procédé étant caractérisée par
B) la fourniture d'un insert de cloison acoustique plan (46) comprenant :
a) une partie acoustique plane (48) possédant une limite droite (52), une limite gauche
(54), une limite inférieure (56) et une limite supérieure (58) ;
b) une partie languette droite (60) faisant saillie à partir de ladite partie acoustique
(48) au niveau de ladite limite droite (52) ;
c) une partie languette gauche (62) faisant saillie à partir de ladite partie acoustique
(48) au niveau de ladite limite gauche (54);
d) une partie languette inférieure (64) faisant saillie à partir de ladite partie
acoustique (48) au niveau de ladite limite inférieure (56) ; et
e) une partie languette supérieure (66) faisant saillie à partir de ladite partie
acoustique (48) au niveau de ladite limite supérieure (58) ;
C) l'insertion dudit insert de cloison acoustique plan (46) dans ladite alvéole (18)
pour former une cloison acoustique (44), ladite partie acoustique plane (48) s'étendant
transversalement auxdites parois supérieure et inférieure (26, 24), ladite partie
acoustique plane (48) possédant un côté supérieur situé au plus près dudit premier
bord (14), un côté inférieur situé au plus près dudit second bord (16) ; et
D) la liaison de ladite partie languette droite (60), de ladite partie languette gauche
(62), de ladite partie languette inférieure (64) et de ladite partie languette supérieure
(66) audit nid d'abeilles (12), ladite partie languette droite (60) étant liée à ladite
partie d'extrémité inférieure droite (30) et à ladite partie d'extrémité supérieure
droite (36), ladite partie languette gauche (62) étant liée à ladite partie d'extrémité
inférieure gauche (28) et à ladite partie d'extrémité supérieure gauche (34), ladite
partie languette inférieure (64) étant liée à ladite partie convexe (32) et ladite
partie languette supérieure (66) étant liée à ladite partie concave (38).
8. Procédé permettant la fabrication d'une structure acoustique (10) selon la revendication
7, ladite partie languette supérieure (66) comprenant un lobe supérieur gauche (66a)
et un lobe supérieur droit (66b) et ladite partie languette inférieure (64) comprenant
un lobe inférieur gauche (64a) et un lobe inférieur droit (64b) ; éventuellement ledit
lobe inférieur gauche (64a) étant séparé dudit lobe inférieur droit (64b) par une
entaille en forme de V (64c), ou
ledit lobe supérieur gauche (66a) et ledit lobe supérieur droit (66b) possédant chacun
un périmètre incurvé (70, 72), ou
ledit lobe inférieur gauche (64a) et ledit lobe inférieur droit (64b) possédant chacun
un périmètre angulaire (74a, 74b ; 76a, 76b) avec un sommet situé au centre (75, 77).
9. Procédé permettant la fabrication d'une structure acoustique (10) selon la revendication
7, des entailles en forme de V (78, 80) séparant la partie languette supérieure (66)
de ladite partie languette droite (60) et de ladite partie languette gauche (62).
10. Procédé permettant la fabrication d'une structure acoustique (10) selon la revendication
7, ladite partie languette droite (60) et ladite partie languette gauche (62) possédant
chacune une extrémité externe formée par un périmètre angulaire (60a, 60b ; 62a, 62b)
avec un sommet situé au centre (61, 63).
11. Procédé permettant la fabrication d'une structure acoustique (10) selon la revendication
7, ledit cloison acoustique (120) étant un maillage acoustique comprenant des fibres
monofilaments dominantes (122) qui s'étendent parallèlement les unes aux autres dans
une direction allant de ladite partie languette inférieure (124) à ladite partie languette
supérieure (126), ou ladite cloison acoustique (120) étant un maillage acoustique
comprenant des fibres monofilaments dominantes (130) qui s'étendent parallèlement
les unes aux autres dans une direction allant de ladite partie languette gauche (130)
à ladite partie languette droite (132).
12. Procédé permettant la fabrication d'une structure acoustique (10) selon la revendication
7, qui comprend les étapes de fixation d'une feuille perméable au son (11) au premier
bord (14) dudit nid d'abeilles (12) et de fixation d'une feuille solide imperméable
au son (13) au second bord (16) dudit nid d'abeilles (12).